Liquid epoxy resin compositions are used widely in the fields of encapsulation, casting, adhesion, and molding since they have excellent curability and ease of handling.
In recent years there have been various changes in the use requirements for liquid epoxy resins. While progress has been made on technology to improve properties, certain properties, such as heat resistance and water resistance, are still not adequate to meet certain use requirements. For example, liquid epoxy resin compositions employing standard curing agents, such as liquid acid anhydrides or amine-type compounds, do not have adequate water resistance. On the other hand, epoxy resin compositions using phenol-type compounds as curing agents provide cured resins having relatively good heat resistance, water resistance and the like, but have the defects that the resulting performances are inadequate. Moreover, since the phenol-type curing agents have very high viscosity or are solids at ordinary temperature, epoxy resin compositions using them also have high viscosity, and as a result, it is difficult to handle the compositions as liquid.
An object of the present invention is to provide a novel liquid epoxy resin composition that can be handled as liquid before curing and gives a cured resin having excellent heat resistance, water resistance, and the like after curing.